Informational only, not legal advice. ADU rules change often and differ by city. Confirm with your local planning department before you rely on anything here.
San Diego has long been one of California's most ADU-friendly cities because of its ADU bonus program, which trades extra units for affordable ones. The 2025 amendments, effective August 22, 2025 outside the Coastal Zone, put lot-size caps on that program and tightened fire rules. This guide walks through San Diego ADU rules as they stand in the September 2026 edition of the municipal code, section 141.0302, so you know what your lot holds before you pay an architect.
Every single-family lot in San Diego can take a converted ADU, a new attached or detached ADU and a JADU, Going beyond that through the bonus program depends on your zone, Sustainable Development Area status, lot size and fire zone. On a lot of 8,000 square feet or less, the hard ceiling is now 4 ADUs and JADUs combined. If you are in the Coastal Overlay Zone, older rules may still apply until the Coastal Commission certifies the changes, so check with Development Services first.
How many ADUs can I build in San Diego?
Single-family lots
On a premises with an existing or proposed house, the code allows one ADU inside the house or an existing accessory structure, plus one attached or detached ADU. One JADU is allowed in single residential zones. That matches the state baseline we describe in the two-ADU rule.
Multifamily lots
On a lot with an existing apartment building, you can convert non-livable space (storage, attics, garages, boiler rooms) into ADUs equal to 25% of the existing units, with a minimum of one. You can also build up to eight detached ADUs, as long as that number does not exceed the existing units. That is SB 1211, written into San Diego's code; our SB 1211 guide runs the math. A proposed new apartment building gets up to two detached ADUs.
Size, height and setbacks
| Rule | San Diego standard |
|---|---|
| New attached or detached ADU | 150 to 1,200 sq ft |
| ADU converted inside house or existing accessory structure | No maximum |
| JADU | Up to 500 sq ft |
| Height on single-family-only lots | Two stories max, and within the base zone height |
| Front setback | Same as base zone |
| Street side setback | 4 ft or the base zone, whichever is less |
| Interior side and rear, 16 ft tall or less | None (4 ft in High or Very High Fire Hazard Severity Zones) |
| Interior side and rear, over 16 ft | 4 ft if next to residential (4 ft in fire zones) |
| Parking | None for standard ADUs and JADUs, with narrow exceptions |
One protection worth knowing: a single ADU of 800 square feet or less is not subject to lot coverage, FAR, front setback or open space limits. The fire marshal can require more; confirm at plan check.
The San Diego ADU bonus program after the 2025 reforms
The ADU Home Density Bonus lets you add a market-rate bonus ADU for each deed-restricted affordable ADU. The current rules:
- Zones. Not available in RS-1-1, -2, -3, -4, -8, -9, -10 and -11 zones unless the lot is in a High or Highest CTCAC Opportunity Area and shown as Residential in a land use plan.
- Inside a Sustainable Development Area, one bonus ADU for every affordable ADU. Outside it, one bonus and one affordable ADU at most.
- Lot-size caps on single-family lots (Table 141-03A, counting all ADUs and JADUs): 4 on 8,000 sq ft or less, 5 on 8,001 to 10,000, and 6 on 10,001 or more. FAR is calculated on no more than 8,000 sq ft of lot area.
- Fire zones. In High and Very High zones the lot must front an improved street with two evacuation routes and cannot be on a cul-de-sac.
- Building costs. Fire sprinklers in every bonus and affordable ADU, one parking space each outside a transit priority area, plus tree and Climate Action Plan rules.
- Affordability terms. 10 years at very low or low income rents, or 15 years at moderate income rents, with the San Diego Housing Commission; breaking it costs at least $10,000 per ADU per month.
- Community Enhancement Fee based on the floor area of the bonus and affordable ADUs, waived for very low and low income units in High or Very High Resource areas.
Sprinklers, parking and fees usually decide whether a bonus project pencils; typical ranges are in our ADU cost guide, and your bids will differ.
Fees, condo sales and pre-approved plans
Under state law, ADUs under 750 square feet pay no impact fees; larger ones pay proportionally (see our impact fee guide). San Diego's permit and plan check fees are in Information Bulletin 501.
San Diego is one of the cities that adopted AB 1033: an ADU can be sold as a condominium once final inspection is complete, with the first 30 days of marketing reserved for buyers who will live in it. Bonus ADUs are excluded; see our AB 1033 guide.
For speed, the city accepts pre-approved plans from the County of San Diego, Chula Vista and Encinitas and reviews them within 30 days, as AB 1332 requires.
Also: ADUs cannot be rented for under 31 days, and new detached ADUs need solar.
How San Diego fits with SB 9 and SB 684
For most single-family owners, the choice is between the bonus program and an SB 9 lot split. The bonus program keeps one lot and requires affordable units; SB 9 creates a second parcel you can sell. On larger multifamily-zoned lots, SB 684 may give more for-sale homes. Run your address in Parcy to compare them, and check San Diego's ADU ordinance and your zone before you design. Not legal advice; a land-use attorney or DSD should confirm the rules for your parcel.
Frequently asked questions
How many ADUs can I build in San Diego?
On a single-family lot you can build one ADU inside the house or an existing accessory structure, one attached or detached ADU, and a JADU. Through the ADU bonus program, the total on a single-family lot is capped at 4 units for lots of 8,000 square feet or less, 5 up to 10,000, and 6 above that.
What are the ADU setbacks in San Diego?
Front setbacks follow the base zone. An ADU 16 feet tall or less needs no interior side or rear setback outside a High or Very High Fire Hazard Severity Zone; a taller ADU next to residential property needs 4 feet, and every ADU in those fire zones needs 4 feet.
How big can an ADU be in San Diego?
A new attached or detached ADU can be 150 to 1,200 square feet. Conversions inside an existing house or accessory structure have no maximum, and a JADU is up to 500 square feet.
Can I sell my ADU separately in San Diego?
Yes, San Diego allows ADUs to be sold as condominiums after final inspection, with a 30-day first offer to owner-occupants. ADUs built under the bonus program cannot be sold separately.
Does San Diego have pre-approved ADU plans?
Yes. The city accepts pre-approved plans from the County of San Diego, Chula Vista and Encinitas, and reviews those applications in 30 days.
Official bill text
- SB 1211 — Land use: accessory dwelling units: ministerial approval. (official bill text, California Legislative Information)
- AB 1332 — Accessory dwelling units: preapproved plans. (official bill text, California Legislative Information)
- AB 1033 — Accessory dwelling units: local ordinances: separate sale or conveyance. (official bill text, California Legislative Information)
Sources
- San Diego Municipal Code §141.0302, ADUs and JADUs (Chapter 14, Article 1, Division 3, 9-2026 edition) — Unit counts, size, height, setbacks, ADU Home Density Bonus, Table 141-03A
- City of San Diego DSD: Accessory Dwelling Unit / Junior Accessory Dwelling Unit — Parking, sprinklers, condo sales, pre-approved plans, 31-day rentals
- City of San Diego DSD: Regulatory Updates — 2025 ADU amendments effective August 22, 2025; 2026 LDC Update adopted June 9, 2026
- City of San Diego Information Bulletin 400: ADU / JADU — Submittal requirements
- Government Code section 66324 (ADU impact fees) — No impact fees on ADUs under 750 square feet
- San Diego ADU rules
- San Diego ADU bonus program
- how many ADUs can I build in San Diego
- San Diego ADU setbacks
- San Diego ADU size limit
- San Diego pre-approved ADU plans
- San Diego ADU height limit
- sell ADU as condo San Diego
- San Diego
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Informational only. Not legal, architectural, or investment advice. Confirm current rules with your local planning department.